A. Field of the Invention
This invention relates to a novel guide for use with staple ring spinning frames of the type wherein the front rolls of the frames are set back from the balloon guide at an angle of at least 10.degree. from vertical. Use of the guide greatly improves the performance of such frames.
B. Description of the Prior Art
The conventional ring spinning frame used in the textile industry for converting sliver to yarn consists of a plurality of identical spinning positions or stations, each having means for drafting the sliver to a desired count and means for twisting and collecting the drafted sliver in the form of yarn. The term "sliver" as used herein includes roving and means a strand of staple fibers having little or no twist. The term "yarn" as used herein means twisted sliver. The drafting means comprises three pairs of driven nip rolls referred to as back rolls, middle rolls and front rolls. Most of the drafting of the sliver occurs between the middle rolls and front rolls. The front rolls forward the drafted sliver from the drafting means to the twisting and collecting means. The twisting and collecting means comprises an upright, rotatable spindle adapted to receive a bobbin, a ring-and-traveler take-up mechanism assoicated with the spindle for inserting twist in the sliver as it is being forwarded by the front rolls and for winding the sliver onto a bobbin vertically mounted on the spindle.
The sliver in passing from the front rolls to the take-up mechanism passes into contact with a guide. The guide is located directly above the spindle and facilitates winding of the sliver onto the bobbin. The length of sliver between the guide and take-up mechanism rotates rapidly about the bobbin axis during operation of the spinning position, forming what is known as a balloon. Typically, the guide is a cylindrically-shaped wire having one end adapted to attach to a spinning frame position and at the other end a coil through which the sliver passes. The coil terminates in a straight piece extending outwardly from the coil to facilitate threading of the sliver through the coil. The coil with its terminating straight piece resembles a "pig's tail" and for this reason the guide is generally referred to as a "pigtail" balloon guide. That portion of the coil's surface over which the sliver makes rubbing contact during operation of the position is referred to as the "yarn contact surface" of the guide.
In practice, the productivity of the spinning position is maximized by operating the spindle at the practical limit of its mechanical capability and then adjusting the peripheral speed of the front rolls so that just enough twist is inserted in the sliver to provide twist in the sliver at the nip of the front rolls so that the sliver will not break at the nip. Increasing the peripheral speed of the front rolls while maintaining the spindle speed constant will increase the delivery speed of the sliver to the traveler, thereby reducing the amount of twist inserted in the sliver which in turn causes the twist in the sliver to move away from the nip and toward the guide. In the absence of twist in the sliver at the nip of the front rolls, the sliver is weakened and pulls apart causing breaks or "ends down". Under normal operating conditions, ends down is caused by imperfections in the sliver (e.g. thin spots). Generally, 30 to 40 ends down per 1000 spindle hours is considered to be acceptable. Of course, it would be economically desirable to improve the performance of the spinning position by reducing the number of ends down per 1000 spindle without sacrificing productivity or by increasing productivity without increasing ends down or both.
U.S. Pat. No. 4,384,448 describes a method of improving the performance of ring spinning positions. The method consists of placing a pneumatic twister on a spinning position between the front rolls and guide, whereby during operation of the position false twist is inserted in the sliver in the same direction as the twist inserted by the traveler. False twist backs up the sliver from the twister into the nip of the front rolls, thereby permitting the position to be operated at higher than normal delivery speeds without increasing ends down or at normal delivery speeds with reduced ends down. In the case of carpet yarn, operating the position at the higher than normal delivery speeds while maintaining the speed of the spindle at its practical limit, provides staple yarn having less twist than normal which enhances the bulk and apparent value of the yarn. However, one drawback associated with using the method described in U.S. Pat. No. 4,384,448 is the cost of the twister and of supplying air to the twister during operation.
Accordingly, it is an object of the present invention to provide a more economical method for improving the performance of ring spinning positions.